This invention concerns a process for the use of hydrogen halides as chain transfer agents in fluoroolefin polymerization.
Chain transfer agents are often added to fluoroolefin polymerizations to lower molecular weight. Applicants have found hydrogen chloride and hydrogen bromide to be highly active chain transfer agents in fluoroolefin polymerizations when these polymerizations are run in the absence of water, the final polymers showing a unique balance of H and Cl or Br end groups. Previously there have been scattered reports of hydrogen chloride and/or hydrogen bromide being used as chain transfer agents, primarily under coordination (Ziegler) polymerization conditions rather than under the radical polymerization conditions reported here or in the polymerization of styrenes.
U.S. Pat. No. 3,472,829 discloses a Ziegler-catalysed process for the polymerization of hydrocarbon alpha-olefins such as ethylene and propylene. Hydrogen chloride is included in a listing of possible chain transfer agents.
U.S. Pat. No. 3,974,237 discloses a Ziegler-catalyzed process for the copolymerization of gaseous hydrocarbon alpha-olefins such as ethylene and propylene to form a block olefinic copolymer. Hydrogen chloride is included in a listing of possible chain transfer agents.
U.S. Pat. No. 3,755,246 discloses a process for the aqueous phase polymerization of vinyl fluoride in the presence of at least one iodine containing compound. The use of hydroiodic acid is disclosed.
U.S. Pat. No. 4,076,699 discloses a process for the polymerization of styrene and substituted styrenes and includes hydrogen chloride in a listing of possible chain transfer agents.
U.S. Pat. No. 5,455,319 discloses the use of iodine-containing chain transfer agents, wherein the iodine is bonded to a primary carbon atom, in the polymerization of a vinyl halide such as vinyl chloride, especially under aqueous emulsion polymerization conditions.
R. N. Hazeldine et al., J Chem. Soc. 3747 (1954) describe the photoinitiated reaction of hydrogen bromide with tetrafluoroethylene to yield Br(CF2CF2)nH, where the product was obtained in yields of (based on HBr) of 66% for n=1, 12% for n=2 and 0.5% for n=3. Similarily, the photoinitiated reaction of HBr with 1-chloro, 1,2,2-trifluoroethylene gave an 85% yield of 1-bromo-2-chloro-1,1,2-trifluoroethane, 4% of 1-bromo-2,4-dichloro-1, 1,2,3,3,4-hexafluorobutane and 0.5% of 1-bromo-2,4,6-trichloro-1,1,2,3,3,4,5,5,6-nonafluorohexane.
This invention provides a nonaqueous process for the preparation of polymers, copolymers, oligomers and telomers of one or more vinyl monomers wherein at least one of the vinyl monomers is partially or fully fluorinated comprising the steps of: a) contacting said vinyl monomer with a HX chain transfer agent, wherein, X is Cl or Br, to form a nonaqueous polymerization reaction mass; b) simultaneously or subsequently further contacting said polymerization reaction mass with a fluoroolefin polymerization initiator; and c) reacting said vinyl monomer to yield said polymer, copolymer, oligomer or telomer.
This invention further provides the products of said process.
This invention provides a nonaqueous process for the preparation of polymers, copolymers, oligomers and telomers of one or more vinyl monomers wherein at least one of the vinyl monomers is partially or fully fluorinated comprising the steps of: a) contacting said vinyl monomer with a HX chain transfer agent, wherein, X is Cl or Br, to form a non-aqueous polymerization reaction mass; b) simultaneously or subsequently further contacting said polymerization reaction mass with a fluoroolefin polymerization initiator; and c) reacting said vinyl monomer to yield said polymer, copolymer, oligomer or telomer.
The vinyl monomers useful in the present invention are those perfluorinated and partially fluorinated monomers subject to radical homopolymerization and copolymerization. Examples include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trifluoroethylene, chlorotrifluoroethylene, hexafluoroisobutylene [(CF3)2C=CH2], vinylidene fluoride (VF2), vinyl fluoride, perfluoroalkyl vinyl ethers, including perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether and perfluoropropyl vinyl ether (PPVE), 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole (PDD), perfluoro (2-methylene-4-methyl-1,3-dioxolane) (PMD) and CF2xe2x95x90CFOCF2CF(CF3)OCF2CF2X, wherein X=CH2OH (EVEOH), xe2x80x94CH2OPO3H2 (EVEOPO3H2), or xe2x80x94SO2F (PSEPVE). This latter sulfonyl fluoride-bearing olefin is a preferred case of the more generally stated monomer CF2xe2x95x90CF(OCF2CFR)aOCF2(CFRxe2x80x2)bSO2F, wherein R and Rxe2x80x2 are independently selected from the group consisting of F, Cl and a perfluorinated alkyl group having 1 to 10 carbon atoms, a is 0,1 or 2 and b is 0 to 6.
Maleic anhydride may be used as a comonomer in the presence of a fluorine containing monomer.
Chain transfer agents useful in the process of the present invention include hydrogen halides: HCl and HBr. HCl is the preferred preferred chain transfer agent.
The amount of HX chain transfer agent used may be from 0.0001 to 50 wt % of total monomers loaded. Chain transfer agent in the amount of from 0.001 to 30 wt % of monomers is preferred. Most preferred is an amount of from 0.002 to 20 wt % of monomers. The amount of chain transfer agent may be adjusted, as is known to those skilled in the art, to allow the desired molecular weight product to be obtained.
The reaction may be carried out in neat monomer, i.e., monomer containing the HX chain transfer agent and the polymerization initiatorxe2x80x94which may be supplied as a solution in a non-reactive solvent. For ease of operation, the process may be carried out in a solvent or diluent, for example carbon dioxide, supercritical or liquid, fluorocarbons, for example, CCl2FCF2Cl, or hydrofluorocarbons, for example CF3CFHCFHCF2CF3. Most preferred is the use of supercritical or liquid carbon dioxide.
Temperatures in the range of from xe2x88x9220xc2x0 C. to 300xc2x0 C. may be employed. A preferred temperature range is from 0 to 200xc2x0 C. Most preferred is a temperature range of from 10 to 50xc2x0 C.
Polymerization intitators employed are those typically used for fluoroolefin polymerizations that are stable in the presence of hydrogen halides. Preferred initiators are perfluorinated diacylperoxides, NF3 and hexafluoropropylene oxide (HFPO) dimer peroxide, [CF3CF2CF2OCF(CF3)Cxe2x95x90OO]2. HFPO dimer peroxide is the most preferred initiator.
This invention further provides the products of the process of the present invention, partially or fully fluorinated polymers and oligomers, as compositions of matter. These products are formed by radical reactions of the type shown below (using TFE as the monomer) in which Xxe2x80xa2 represents a halogen radical such as bromine or chlorine radicals and in which Ixe2x80xa2 represents an initiating radical such as CF3CF2CF2OCF(CF3)xe2x80xa2 from HFPO dimer peroxide.
xe2x80x83Ixe2x80xa2+n CF2xe2x95x90CF2xe2x86x92Ixe2x80x94(CF2CF2)nxe2x80xa2xe2x80x83xe2x80x83(1)
2Ixe2x80x94(CF2CF2)nxe2x80xa2xe2x86x92Ixe2x80x94(CF2CF2)nxe2x80x94(CF2CF2)nxe2x80x94Ixe2x80x83xe2x80x83(2)
Ixe2x80x94(CF2CF2)nxe2x80xa2+HXxe2x86x92Ixe2x80x94(CF2CF2)nH+Xxe2x80xa2xe2x80x83xe2x80x83(3)
Xxe2x80xa2+n CF2xe2x95x90CF2xe2x86x92Xxe2x80x94(CF2CF2)nxe2x80xa2xe2x80x83xe2x80x83(4)
Xxe2x80x94(CF2CF2)nxe2x80xa2+HXxe2x86x92Xxe2x80x94(CF2CF2)nH+Xxe2x80xa2xe2x80x83xe2x80x83(5)
Xxe2x80x94(CF2CF2)nxe2x80xa2+CF2xe2x95x90CF2xe2x86x92Xxe2x80x94(CF2CF2)n+1xe2x80xa2xe2x80x83xe2x80x83(6)
2Xxe2x80x94(CF2CF2)nxe2x80xa2xe2x86x92Xxe2x80x94(CF2CF2)nxe2x80x94(CF2CF2)nXxe2x80x83xe2x80x83(7)
The higher the concentration of HX, the more likely reactions (4), (5), and (6) are to cycle repeatedly, making the product of equation (5) the predominant species in the reaction mixture and the numbers of H and X ends approach equality. The lower the concentration of HX, the greater the extent to which ends will be determined by the initiation step, equation (1), and the termination reactions, equations (2) and (7), thus increasing the fraction of initiator derived ends, lowering the fraction of H ends, and increasing the ratio of X ends to hydrogen ends.
Thus, the compositions of the present invention are partially or fully fluorinated polymers and oligomers of the structure X-(monomer)n-H. The polymer chains have on average 0.6 to 1.0 H end groups and 0.6 to 1.0 X end groups, wherein X is chorine and/or bromine. More preferably chains average 0.9 to 1.0 H end groups and 0.9 to 1.0 X end groups. Most preferably chains average 0.95 to 1.0 H end groups and 0.95 to 1.0 X end groups. The balance of any ends not H or X are ends derived from initiator and any ends derived from chain transfer/radical abstraction with other components in the reaction mixture. Overall there are a total of two end groups per chain consisting of the sum of the H ends, the X ends, ends derived from initiator, and any ends derived from chain transfer/radical abstraction with other components in the reaction mixture.
An alternate representation of the compositions of the present invention is X1xe2x88x92yxe2x80x94Yy(monomer)n-H1xe2x88x92zYz, wherein Y represents the non-X and non-H end groups, wherein Y is made up of initiator and any ends derived from chain transfer/radical abstraction with other components in the reaction mixture, and the values of y and z are, independently, between 0 and 0.4, preferably between 0 and 0.1 and most preferably between 0 and 0.05.
For purposes of the above discussion, polymer products are discussed in terms of linear polymers. As known to one skilled in the art, small amounts of branched polymers may be formed due to the presence of small amounts of impurities or branch-forming reactions. Compositions containing minor amounts of said branched polymers are meant to be within the scope of this invention.
In the formula X-(monomer)n-H, preferred monomers include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trifluoroethylene, chlorotrifluoroethylene, hexafluoroisobutylene ((CF3)2Cxe2x95x90CH2), vinylidene fluoride (VF2), vinyl fluoride, perfluoroalkyl vinyl ethers, including perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether and perfluoropropyl vinyl ether (PPVE), 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole (PDD), perfluoro (2-methylene-4-methyl-1,3-dioxolane) (PMD), CF2xe2x95x90CFOCF2CF(CF3)OCF2CF2X, wherein Xxe2x95x90CH2OH (EVEOH), xe2x80x94CH2OPO3H2 (EVEOPO3H2), or xe2x80x94SO2F (PSEPVE), CF2xe2x95x90CF(OCF2CFR)aO(CF2)b(CFRxe2x80x2)cSO2F, wherein R and Rxe2x80x2 are independently selected from the group consisting of F, Cl and a perfluorinated alkyl group having 1 to 10 carbon atoms, a is 0, 1 or 2, b is 0 to 6 and c is 0 or 1; and, as a comonomer with one or more fluorinated monomers, maleic anhydride.
Copolymers of the present invention bearing pendant sulfonyl fluoride groups may be converted by modification of known hydrolysis methods to ionomers. The counter ion of the hydrolyzed sulfonyl chloride group may vary widely as is known in the art and may be selected from alkali metals, for example sodium or lithium.
In the formula X-(monomer)n-H, values of n may be in the range of about 5 to 20,000, preferably 20 to 1000, most preferably 25-100.
The compositions of the present invention are useful as lubricants and as synthetic precursors to surfactants, macromonomers and polyelectrolytes.